1. Field of the Invention
The present invention relates to a TFT (Thin Film Transistor) formed over a substrate.
2. Description of the Related Art
In accordance with the reduction in scale of an integrated circuit, the contact resistance between Si and metals as well as the resistance of source and drain regions has been required to be lowered. Ti or Co silicide has been adopted for the LSI process. Meanwhile, since Ni silicide (NiSi) can be formed at a low temperature, it is researched as a next-generation material.
For example, a Ni silicide formation step in a TFT manufacture process is carried out by depositing a Ni film over a source region and a drain region by sputtering and then annealing the Ni film at about 450° C. so that an unreacted portion of the Ni film is removed (see Patent Document 1).
In this manner, the Ni silicide formation step has conventionally been carried out by:
(1) forming a Ni film over a semiconductor film;
(2) applying heat treatment to produce Ni silicide by chemical reaction; and
(3) removing an unreacted portion of the Ni film.    [Patent Document 1] Japanese Patent Laid-Open No. 2004-221115.
When the aforementioned process is carried out, the number of manufacturing steps is inevitably increased. The increase in the number of manufacturing steps is preferably suppressed since it will lead to a higher cost, shipping delay, higher probability of troubles, lower yield and the like.
Further, in the aforementioned steps, the thickness of the silicide film is determined by three parameters that are the thickness of a Ni film, the heat treatment temperature and the heat treatment time; therefore, elaborate conditioning and management of the treatment conditions are required in order to accurately control the thickness of the silicide film.